Types of Url patterns?

Url-pattern is the name which is used by the client to communicate with a servlet or even a jsp.  Url-patterns can be specified in the following ways.
1)      Exact match method
2)      Directory match
3)      Extention match
1)Exact match
            This method required the url-pattern to start with slash '/' and should not end with star '*' .
            Ex:  <url-pattern>/sample/first</url-pattern>
2)Directory match
            In this method the url-pattern should start with a slash '/' and usually terminates with a star '*' .
            Ex:  <url-pattern>/sample/*<url-pattern>
3)Extention match
            In this method the url pattern should not start with a slash '/'.
            Ex:  <url-pattern>*.do</url-pattern>